1. DELIVERING MICROWAVE SPECTROSCOPY TO THE MASSES: A DESIGN OF A LOW-COST MICROWAVE SPECTROMETER OPERATING IN THE 18-26 GHZ FREQUENCY RANGE Amanda L. Steber and Brooks H. Pate Department of Chemistry, The University of Virginia, Charlottesville,VA 22904

2. Introduction Goal: Create a spectrometer that the general public can use in a museum exhibit in order to get them interacting with spectroscopy in the context of astrochemistry What considerations have to be made? ◦ Size ◦ Power consumption ◦ Cost ◦ Vacuum ◦ Durability ParameterCurrent Spectrometers Museum Requirements SizeLargeSmall Power Consumption HighWall source VacuumRigorousStatic CostCan be >$100,000 Minimal <$10,000 DurabilityHigh

3. Advances in Technology Monolithic microwave integrated circuits (MMICs) ◦ Typically operate from 300 MHz to 300 GHz ◦ Mixing, switching, amplification ◦ Mass produced ◦ Low cost ◦ Small ◦ High Reliability Where they are used ◦ Cell phones ◦ Computers ◦ Cars ◦ Televisions

4. How can this work to our advantage? TiePie Handyscope HS5 ◦ 240 MS/s AWG ◦ 32 MSamples per channel ◦ 200 MS/s Digitizers ◦ 12 bit Valon 5008 ◦ Dual channel Synth ◦ 138-4400 MHz Wave Gen Xpress ◦ 8 MB memory buffer ◦ 16 “driver” channels ◦ Accepts 100 MHz external clock (10 ns resolution) Intel NUC ~$600 ~$395 ~$1650 ~$670

5. Spectrometer

6. Dimensions ◦ Gas cylinder: ~3 ft Key Features: ◦ Phase coherence ◦ Real time averaging (100 FIDS at a time) 10  s Acquisitions 100 Acquisitions at a time (potential to do more)

8. Spectroscopic Details Long term vacuum ◦ Signals have held up for over a month now 50 cm length of waveguide ~2 W of power Ammonia: 3(3)a – 3(-3)s at 23870.13 MHz ◦ 800:1 S/N in 100 averages OCS: 2-1 at 24325.927 MHz ◦ ~200:1 in 100 avg Water 6 16 -5 23 at 22235.044 MHz ◦ 80:1 in 100 avg

9. Bringing Spectroscopy to the Masses

10. Programming Python 2.7 ◦ PyQt ◦ PyQtGraph Simulation Mode vs Experimental Mode ◦ Can be run in simulation mode in case during transport something is damaged ◦ Experimental mode is full operation in which a real spectrum is displayed

11. Graphical User Interface

13. Conclusions A small, compact spectrometer has been built that can hold vacuum for longer than one month The python programmed GUI allows users to select which molecule they would like to take a spectrum of in real time This may lead to more interest in the field along with amateur astrochemists working on projects such as Citizen Sky or Planet Hunters

14. Acknowledgements Pate Lab NSF funding ◦ DRL Award Number 1118579 ◦ Centers for Chemical Innovation Award Number 0847919